MUS 312 Form & Analysis

K. Scale Formations in 20th-Century Music

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Five-Note Scales

Pentatonic--generic term for all five-note scales.  However, when one refers to the pentatonic scale, the following pattern is usually the one that is meant:  C-D-E-G-A, or any pattern equivalent to the black keys on a keyboard.  This scale uses only major 2nds and minor 3rds.  It is also referred to as the anhemitonic pentatonic scale (anhemi meaning the absence of "half" steps).  Of course, any member of the pentatonic scale may serve as the tonic; thus, five "modes," or rotations, are possible.  Naturally, the pentatonic scale may be transposed.

The pentatonic scale is a limited source of melodic pitch material, and it is also limited in its tertian harmonies.  From the above pentatonic scale, the only tertian chords that could be constructed are triads on C and A, and a minor 7th chord on A.  This means that the accompaniment to a pentatonic melody will probably be either nontertian or nonpentatonic, or both.

Other versions of the pentatonic scale are possible--versions employing minor 2nds and major 3rds--but they occur less often in Western music.

Six-Note Scales

The only six-note scale to see much use in the 20th century is the whole-tone scale.  It is constructed entirely of major 2nds (and a diminished 3rd, which sounds like a major 2nd).  Only two whole-tone scales are possible; any other transposition will duplicate the pitch-class content of one of the scales.  (The actual spelling of the scale is irrelevant.)

The whole-tone scale is more limited both melodically and harmonically than the pentatonic scale.  No major or minor triads are possible, and the only 7th chords available are the dominant 7th with the lowered 5th (French augmented-6th sonority).

Seven-Note Scales

Modal scales have been enthusiastically rediscovered by a number of 20th-century composers.

Major modal scale patterns:

  • Ionian:  same as a major scale
  • Dorian:  same as natural minor with a raised 6th
  • Phrygian:  same as natural minor with lowered 2nd
  • Lydian:  same as major with a raised 4th
  • Mixolydian:  same as major with lowered 7th
  • Aeolian:  same as natural minor
  • Locrian:  same as natural minor with lowered 2nd and lowered 5th.

Identifying transposed modes:

(Note: You will not always be able to identify the scale being used just by determining the "tonic" and looking at the key signature, because not all composers use modal key signatures.)

  1. The final of the Ionian mode is the 1st scale degree of the major key signature.
  2. The final of the Dorian mode is the 2nd scale degree.
  3. The final of the Phrygian mode is the 3rd scale degree.
  4. The final of the Lydian mode is the 4th scale degree.
  5. The final of the Mixolydian mode is the 5th scale degree.
  6. The final of the Aeolian mode is the 6th scale degree.
  7. The final of the Locrian mode is the 7th scale degree.

Other Seven-Note Scales

Many other 7-note scales are possible, although none of them have been used as frequently as the diatonic modes.

Eight-Note Scales

Octatonic, like pentatonic, is a generic scale that has nevertheless come to refer to a specific scale.  Also called the diminished scale, the octatonic scale consists of alternating major and minor 2nds, hence, the third name: whole-step--half-step scale.  There are only two modes to this scale--one begins with a major 2nd, the other with a minor 2nd--and only three transpositions.  The actual spelling of the scale is optional in terms of enharmonics.

The octatonic scale is a rich source of melodic and harmonic material.  It contains all of the intervals, from the minor 2nd to the major 7th.  All of the tertian triads, except for the augmented triad, can be extracted from this scale, as can four of the five common 7th-chord types--no major 7th chord.

Chromatic Scale

Many musical passages in the 20th century avail themselves of all or nearly all of the tones of the chromatic scale.  In some cases it is only the harmony or only the melody that is chromatic, while in other cases both are.

Microtonal Scales

In modern usage, microtone means any interval smaller than a minor 2nd.  Microtones were first used in the music of ancient Greece and were mathematically defined by the theorists of that time.  In any case, microtones like the diatonic modes, have been rediscovered in the 20th century by composers who have used them in new and varied ways.  In most cases, microtone usage has employed quarter-tones (half the size of a minor 2nd); however, other microtonal intervals have been used as well.

Other Possibilities

In addition to the above scales, there are always other possibilities.  Messiaen, e.g., has developed what he calls "modes of limited transposition."  These are scales of from 6-10 notes that have fewer than twelve transpositions without duplication of pitch-class content.  Other possibilities would include simultaneous use of more than one scale, etc.

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